The initial intervention and the type of treatment depend upon location of the stenosis, wall integrity, length, and severity, as well as to the presence of comorbidities and overall health status of the patient.

Traditionally, surgery has been the mainstay of treatment, with excellent results in 90% of cases [2–4]. However, surgery is not always de nitive and there is a percentage of recurrence that can reach 10% in some series [5]. Surgery involves some risks, and associated complications have been reported to be greater than 8–12% with a mortality rate of 5% [6, 7]. Although in recent years, complications and mortality rates have decreased due to an improvement in surgical techniques, intraoperative and postoperative care [8]. Moreover, many patients are unable to undergo a surgical procedure because of underlying cardiopulmonary limitations and there is a non-depreciable number of patients that refuse the surgery. Endoscopic management of tracheal stenosis provides a safe and ef cient therapeutic option and is often the rst-line therapy in patients who are not appropriate surgical candidates or who have failure after airway resection. Several modalities have been used to relieve endoluminal obstructions, including mechanical approaches such as dilatation with a rigid bronchoscope or with balloon; heat-related modalities such as laser, electrocautery, and argon plasma coagulation; contact probe cryotherapy; and a variety of airway stents [9, 10].

Drug therapy combined with endoscopic treatment, as systemic steroids [11], intralesional injection of corticosteroids [12], topical application of mitomycin-C [13, 14], or other drugs as paclitaxel [15], is another option in the treatment of this pathology but experience is very limited and results are variable. So far none of these last treatments are curative.

Etiology

Congenital Tracheal Stenosis

Congenital tracheal stenosis is a rare but underdiagnosed anomaly which can present as life-­ threatening respiratory insuf ciency in neonates

and infants. Congenital anomalies are the most common cause of airway narrowing in the pediatric population. They are rare malformation, produced by the absence of most of the membranous portion of the trachea in the affected segment, and the cartilaginous rings extend along the entire circumference of the tracheal wall. Three anatomical types have been described which are as follows:

\(a)\ Generalized stenosis, from the cricoid to the carina with possible bronchial involvement; \(b)\ Infundibular stenosis, where part of the trachea, proximal or distal, has a normal caliber. \(c)\ Segmental stenosis, with involvement of a

short portion of the trachea.

These malformations can appear alone or, very often, associated with other abnormalities of the bronchovascular tree and other organ malformations, of which the most frequently seen is esophageal atresia [16].

Cardiac anomalies are frequently associated and may be addressed at the time of tracheal surgery.

Management of congenital stenosis is very challenging. Children can present stridor, recurrent pneumonia, cyanosis, wheezing, and sometimes respiratory failure.

Corrective surgery is the treatment of choice; in short stenosis, resection of the compromised segment and anastomosis is the best option. When the stenosis affects long segments of the trachea, anastomosis becomes dif cult for excessive pressure on the suture line and the endoscopic approach can be an effective alternative to help these patients.

Iatrogenic

The causes of postintubation and post-trache- ostomy tracheal stenosis are well established. Endotracheal tube (ETT) causes pressure injury to the glottis, subglottis, and tracheal mucosa and may result in severe scarring.

Physiologically, the healing of the ulcer formed by the cuff pressure in the mucosa

involves regenerating epithelium (primary healing) and repair (secondary recovery), but sometimes the regeneration of the epithelium does not occur and leads to an overgrowth of granulation tissue. Eventually, the tissue subsequently becomes avascular resulting in a brous scar stricture.

Postintubation tracheal stenosis was recognized for the rst time as an entity in 1880, after MacEwen instituted prolonged endotracheal intubation as a therapy in four patients with main airway obstruction [17].

Since then, many reports have been published on serious complications resulting from postintubation stenosis (PIS) or post-tracheostomy stenosis (PTS). The rate of presentation varies: among all intubated patients, 0.6–21% will develop tracheal stenosis. PTS in turn can present from 6 to 21% of all patients that have undergone tracheostomy [7, 17, 18]. Only a minority of them (1–2%) will present with symptoms or severe stenosis [19].

Currently, the calculated incidence of moderate or severe stenosis resulting from endotracheal intubation or tracheostomy is estimated at 4.9 cases per million per year in the general population [20].

Prolonged tracheal intubation can produce tracheal stenosis at many tracheal levels [21] from the tip of the endotracheal tube to the glottic and subglottic area, but the most affected places are the level of the endotracheal tube (ETT) cuff and around the stoma in tracheostomized patients.

The development of the stenosis has many stages; at the beginning there is mucosal ulceration due to decreased blood fow at the level of contact with the ETT cuff. Then, cartilage exposure and perichondritis develop, followed by granulation tissue formation, which over time becomes an established brous stenosis, which can be more or less xed. In the worst cases, cartilage destruction occurs and the airway wall loses its support.

PTS usually affects the area of the stoma, where the tracheostomy tube curves down, following the same sequence mentioned above. Sometimes granulation tissue is formed above

Fig. 15.1  Post-tracheostomy tracheal stenosis

the bend of the tube and progresses toward brosis [22, 23].

The presence of infection, very common in ventilated patients (tracheitis, mucositis), is a contributing factor for the development of airway stenosis [24]. A common nding in post-­ tracheostomy patients is retraction of the tracheal cartilage at the area of the tracheostomy, producing different degrees of stenosis (Fig. 15.1). Surgery is the treatment of choice in these situations. When the patient is not a surgical candidate, an airway stent may be bene cial.

Percutaneous tracheostomy is a procedure that is increasingly indicated in the critically ill patient, and although the long-term complications of this procedure are infrequently mentioned in the literature, some published data suggests that the rate of tracheal stenosis is signi cantly higher than reported [25].

A publication on 100 patients that underwent percutaneous tracheostomy revealed that major postoperative complications presented in 2.4% of cases, and these included death, cardiac arrest, loss of the airway, pneumothorax, tracheoesophageal stula, and injury to the posterior wall of the trachea (mucosal tear). Tracheal stenosis was reported in 31% of patients, 20% of which were symptomatic [26].

Other studies showed better results. Van Heurn et al. [27] found an index of stenosis greater than 10% in 26% of 80 decannulated patients after percutaneous tracheostomy, being moderate in 4% of the cases, and severe in 2%. Hill et al. [28] revealed that 8 of 214 (3.7%) patients with percutaneous tracheostomies developed symptomatic tracheal stenosis.

Therefore, iatrogenic airway injury after endotracheal intubation and tracheostomy continues to be a serious clinical problem.

In fact, nowadays because of the coronavirus disease (severe acute respiratory syndrome coro- navirus-­2 [SARS-CoV-2]) pandemic with an increase in intensive care unit (ICU) admission of patients with bilateral pneumonia (11% of all cases of pneumonia) [29], requiring prolonged intubation and tracheostomy, it is feared that an increase in cases of iatrogenic tracheal stenosis could be happened [30].

In addition to the most frequent causes of postcoronavirus disease 2019 (COVID-19) dyspnea such as interstitial or vascular alterations [31], this entity should be considered in patients with persistent dyspnea after prolonged admission in the ICU due to bilateral COVID-19 pneumonia. Some case reports with a few cases have been published since the end of the rst wave [32–34].

In these patients, endoscopic treatments may be more relevant, because they can be in a poor physical situation or in a recovery phase.

Infectious

Many airway infections can cause damage to the tracheal mucosa, resulting in stenosis. Tuberculosis (TB), fungal infections, bacterial tracheitis, histoplasmosis, and diphtheria are some of them, being TB the most frequently seen.

TB is the most common infectious cause of airway stenosis. It usually produces distal stenosis (at the level of the bronchi), but central airway stenosis can also occur. This complication can present at the time of the active infection or long after that, up to 30 years [35]. The most important risk factor for developing airway stenosis is the presence of TB bronchitis, which

is found in 10–37% of patients with pulmonary TB when bronchoscopy is performed [35, 36] In those cases, over 90% of patients will develop tracheobronchial stenosis in spite of correct TB treatment [37].

Infectious stenosis is more prevalent in underdeveloped countries, particularly in Asia and Africa. Active infection produces necrosis and ulceration of the bronchial mucosa, giving rise to granulation tissue and subsequent brous stenosis.

During brous, established stenosis, dilatation of the lesion is an option. When the stenosis occurs at bronchial level, balloon dilatation can be offered. At tracheal level, rigid bronchoscope dilatation is useful as well. Repeated dilatations or stent placement are often required, since recurrence rate is very high.

Idiopathic Tracheal Stenosis

The term idiopathic tracheal stenosis (ITS) is used to include patients with tracheal stenosis when all other etiologies have been investigated and ruled out.

ITS is a rare condition, characterized by circumferential brous stenosis beginning at the subglottic area and compromising the proximal segment of the trachea [38]. Typically, it affects women in their third to fth decade, so it is thought that estrogens could play an important role [39]. Another hypothesis is that it is related to gastroesophageal refux [40]. Clinically ITS is presented with months to years of symptoms such as progressive dyspnea, wheezing, stridor, or a combination of all of them. In many cases, patients are misdiagnosed as dif cult to treat asthmatics [41].

Grillo et al. [41] presented 49 patients with tracheal stenosis where no etiology was found after extensive evaluation. They highlighted the need to pay special attention to the airway in chest radiographs or computerized tomographies when evaluating a patient with a history of prolonged dyspnea and wheezing. Also, the fow-­ volume curve and the bronchoscopy are essential for diagnosis.

Surgery remains the treatment of choice [42]. Some authors have shown that endoscopic treatment with mechanical dilation or associated with laser or electrocoagulation and stent placement could be ef cient, but with recurrences during the follow-up, that also can be treated with endoscopic procedures [43].

Bronchial Stenosis Post-lung

Transplantation

Since the rst lung transplant in 1963, technical advances in thoracic surgery along with new immunosuppressive agents have made lung transplantation a more common indication for those patients with terminal lung disease. However, one of the main problems of this surgical procedure is the development of stenosis at the level of the suture.

Perianastomotic stenosis occurs in 12–40% of patients and nonanastomotic distal bronchial stenosis in 2–4% of all lung transplants [44, 45].

Bronchial stenosis is related to airway infammation, with mononuclear cell injury to the epithelium and mesenchyme that is further complicated by endothelial injury on a poorly vascularized area. The severe blood-fow impairment may lead to bronchial cartilage ossi cation, calci cation, or fragmentation, leading to stenosis [46].

Other factors increase the risk for suture stenosis, such as the use of a simple suture and prolonged mechanical ventilation. There is a very high risk of suture infection also due to low blood fow and the presence of infammation. Infection should be looked for and appropriately treated before performing any endobronchial manipulation, particularly if a stent placement is considered.

Success depends primarily on the experience of the interventional pulmonology team and the medical resources available.

Distal Bronchial Stenosis

As mentioned previously, bronchial stenosis secondary to pulmonary tuberculosis is quite

Fig. 15.2  Bronchial stenosis of the right upper lobe

common. Approximately 43% of patients with pulmonary tuberculosis will develop stenosis at the distal bronchi [47, 48] (Fig. 15.2). This number corresponds to approximately 4.1% of all bronchoscopies performed in a hospital.

Another cause for distal stenosis is bronchial anthracosis (called anthracostenosis) [49, 50].

As a result of bronchial stenosis, there exists dif cult drainage of secretions and recurrent infections distal to the obstruction, with the development of bronchiectasis. In these situations, it is indicated to offer a dilatational therapy that can be performed via balloon dilatation with or without laser application. This treatment is simple to apply, and can be easily performed during a short procedure. It has good results, improving secretions clearance which in turn prevents repeated infections. In addition to bronchoscopy, threedimensional helical tomography of the tracheobronchial tree can be very useful in the evaluation of this condition, since it allows a better distal inspection than bronchoscopy [51].

Another less common cause of airway stenosis is radiation therapy. The incidence of bronchial stenosis has increased following treatment with brachytherapy or external beam radiotherapy of malignant lesions of the airways, with an estimated incidence of 9–12% [52].

Bronchial stenosis is established within an average of 40 weeks after initiation of radiother-